In some multiprocessor systems, processors in a group can coordinate their operational sequences. One such sequence, for example, is referred to as a join. A join, in some implementations, is a process where several execution threads on respective processors are required to deliver their results to a serialized execution sequence, which can proceed only when all of the threads have completed. In some implementations, processors in a group employ a barrier operation that ensures that such processors reach a common synchronization point before proceeding. Processors can use specialized barrier instructions to control barrier operation.